The overall objective of the proposed research is to gain greater understanding of protein-protein and protein-RNA interactions in tobacco mosaic virus (TMV) and of the interactions of virus, protein and RNA with electrolytes. A major aspect is to continue and extend the current study on the contribution made by electrical work terms, salting-out and hydrogen ion binding to the entropy-driven polymerization of (TMV) protein. This will be done primarily by studying the effect of ionic strength and pH on the equilibrium involved in the polymerization, using protein from strains of TMV with known differences from the type strain in amino acid composition. The results will be analyzed through the use of theory developed in current studies. A second aspect is to investigate, more fully than has been done up to now, the difference between the type of polymerization at pH values near neutrality which involves hydrogen ion binding and that which does not. Polymerization and depolymerization experiments in totally unbuffered systems will be carried out on proteins from the type strain and from other strains such as Dahlemense and E66. Current studies on the binding of calcium ion by TMV and TMV protein will be extended to include TMV-RNA. Other ions will also be investigated. The primary method of study will be electro-chemical, using ion specific electrodes.